Sump pump

ABSTRACT

A sump pump of especially simple, inexpensive construction employing primarily molded plastic components, other than the electrical drive motor and associated components, comprising a novel assembly of molded plastic components in which adequate motor heat dissipation is provided by a metallic heat sink arrangement, and in which novel structural features are provided including a floating drive shaft bearing arrangement and a novel carrying handle utilizing the electrical power conductors for the drive motor as a part of the handle structure.

llnite 1 States atent 1 1 Cade et al. July 9, 1974 [54] SUMP PUMP3,637,326 1/1972 Dowell 417/44 3,653,785 4 1972 1) 111 417 424 [751Inventors: Gemge Cade; Beach; 3,685,926 23/1972 811m 417424 Fliesen, 0fProphetstown, 111-; 3,694,110 9/1972 Guinard 417/424 Samuel R. Phillips,San Francisco,

Calif.

[73] Assignee: Houdaille Industries, Inc., Buffalo,

[22] Filed: July 21, 1972 [21] Appl. No.: 273,949

[52] US. Cl. 417/368, 417/372 [51] Int. Cl. F04b 39/06 [58] Field ofSearch 417/38, 422, 424, 44

[56] References Cited UNITED STATES PATENTS 3,246,186 4/1966 Schaeffer417/422 3,307,000 2/1967 Ekey 1 417/44 3,327,144 6/1967 Double 417/4223,556,677 1/1971 Treman .1 417/44 Primary Examiner-William L. FreehAttorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman,Chiara & Simpson ABSTRACT A sump pump of especially simple, inexpensivecon struction employing primarily molded plastic components, other thanthe electrical drive motor and associated components, comprising a novelassembly of molded plastic components in which adequate motor heatdissipation is provided by a metallic heat sink ar rangement, and inwhich novel structural features are provided including a floating driveshaft bearing arrangement and a novel carrying handle utilizing theelectrical power conductors for the drive motor as a part of the handlestructure.

2 Claims, 4 Drawing Figures SUMPPUMP BACKGROUND OF THE INVENTION Thepresent invention is directed to a pump structure, more particularly asump pump, utilizable as a submersible pump, and completely immersiblein the liquid, normally water, to be pumped. In the pastsump pumps ofthe type herein involved have'been constructed principally of metal andto insure reasonably long life and operation many of the component partsthereof were made of bronze or other suitable metal which would moreeffectively resist rust and corrosive actions resulting from theimmersion of the pump structure in the pumped liquid. With the attendanthigh cost of this type of construction, some efforts have been made inthe past to reduce costs by the use of plastic in. lieu of metalcomponents, such transition to plastic components primarily involvingthe substitution of plastic for metal, i.e. fabricating components ofsubstantially the same configuration as that previously emthereon ahandle member by means of which the pump may be carried and transported,with the connecting conductor cord thus forming a part of the handlestructure, thereby eliminating additional handle connecting components,joints, etc.

The motor housing structure is adapted to support a suitable bearing, asfor example a ball bearing which is disposed adjacent the impeller endof themotor drive shaft and adapted to maintain the adjacent end of theshaft in operable position, both radially and axially, with the bearingthus forming the shaft axial-aligning means. The opposite end of theshaft is supported in a suitable bearing, which may be a sleeve bearing,whereby the shaft is maintained in radially fixed relation with respectto the motor stator core, ect. but

floating as to axial movement of the shaft, whereby the ployed butproduced from plastic materials instead of metal, and employing standardmotor structures.

The present invention is directed to a pump structure of the typedescribed which is specifically designed for fabrication, substantiallycompletely from plastic material, with the exception of motor componentsnecessarily of metal, and associated components required for the supplyand control of electrical power to the motor.

BRIEF SUMMARY OF THE INVENTION The present invention is. directed toproduction of a sump pump which overcomes the problems referred to, inwhich substantiallyall of the components of the pump are constructed ofplastic, other than the motor drive shaft, rotor, stator, fieldwindings, bearings and necessary power cords, switches, etc. In thefinal assembly, only two main plastic subassemblies are employed, oneinvolving the motor structure, etc. and the other the base and pumpstructure. I

The motor structure may comprise merely three' plastic components, whilethe base and pump assemblyv may comprise a base member, two pump halvesand a cooperable pump impeller. The base unit may also form thereceptacle for a pressure operable switch by means of which the motormay be controlled in dependence upon the presence or absence of liquidto be pumped.

Power is adapted to be supplied to the pump by a power cord which an endof operably'terminates at the switch receptacle, and a connecting cordwhich extends from the switch receptacle to the motor housing and isadapted to complete the circuit, from the switch receptacle and powercord; to the 'motor. The respective cords are suitably connected totheir associated receptacle or housing in fluid-tight relation, and theconnecting conductor cord is adapted to have mounted shaft is supportedin axially fixed relation merely at the lower bearing, thus maintainingthe impeller in substan tially axially fixed relation but permitting themain body of the shaft, and the rotor carried thereby, to shift axiallyin response to thermal expansion and contracform of a metallic memberforming the partition wall between the interior of the motor housing andthe intake chamber of the base structure. The rotor is provided withsuitable fins at its lower end to promote oil circulation in the motorhousing whereby an effective heat transfer will take place through thewall forming the heat sink between the oil and the water or other liquidbeing pumped.

BRIEF DESCRIPTION OF THE DRAWINGS power cord construction and cooperabletest device.

DETAILED DESCRIPTION OF A PREFERRED I EMBODIMENT OF THE INVENTIONReferring to the drawing and more particularly to FIGS. 1 and 2, thepump structure therein illustrated,

designed as a submersible type sump pump, comprises a base member 1 ofsuitable molded plastic adapted to contain a vortex pump 2 operativelycommunicating with a water discharge outlet 3 in the upper face 4 of thebase unit, and likewise formed from molded plastic.

Carried by and extending upwardly from the base unit is a molded plasticmotor housing, indicated generally by the numeral 5, illustrated asbeing constructed in two sections, an upper section 6 and a' lowersection 7, with the housing being adapted to suitably support therein anelectric motor, indicated generally by the numeral 8. Also extendingupwardly from the base 1 and illustrated, in the present embodiment ofthe invention, as being integrally fonned therewith is a switch housingindicated generally by the numeral 9, adapted to receive a pressureresponsive switch indicated generally by the numeral 10.

Power from a suitable power supply line is adapted to be supplied to thepump through a power cord, indicated generally by the numeral 11, whichis connected to the pump structure at the switch housing 9, with powerbeing adapted to be conducted from the power cord 11 and switch to themotor 8 through a connecting cord, indicated generally by the numeral12, which carries a handle member 13 by means of which the pump may bemanually carried.

Referring to FIGS. 2 and 3, the plastic base 1 is provided withperipheral upstanding walls 14, which with the top wall 4, are operativeto form a water intake chamber 1, the lower wall of which is adapted tobe defined by the surface upon which the pump may be disposed duringoperation, with a suitable portion of the side walls 14 being providedwith openings 15 therein, illustrated as being in the form of verticallyextending slots, which cooperably from the intake opening for water intothe intake chamber 1 of the base.

The pump 2, disposed in the chamber 1 is illustrated as beingconstructed in the form of two cooperable plastic halves, a lower halfand an upper half 2b which are mechanically fastened by means of screwsor the like along their mating edges to form a unitary structure. Thepump 2 may be of generally standard mechanical design comprising a pumpcasing 16, of suitable configuration, which operatively communicateswith the water discharge outlet 3 through a discharge vortex 17, thefree end 18 of which is suitably flanged or otherwise formed andcemented of solvent welded to the internally threaded outlet fitting l9,integrally formed on the base 1. Disposed in the central well portion 20of the casing 16 is a molded plastic rotaty impeller 21, likewise ofsuitable configuration and having its central hub portion 22 rigidlysecured to the adjacent end 23 of the drive shaft 24 of the motor 8.Relative rotation of the impeller and shaft is prevented by a suitableflat on the face of the shaft and complementary projection in the boreof the impeller, with the latter being retained in operative position bya lock screw 25, threaded into the end face of the motor drive shaft.The casing 16 is provided with a water inlet opening 26 disposed on theupper face of the pump casing and communicating with the water intakechamber 1 formed by the base 1. Thus, water entering the intake opening15 may flow through the intake opening 26 of the pump and, with suitablerotation of the impeller 21, discharged through the discharge vortex 17and discharge opening 3 for conduction through a suitable conduitthreaded into the internally threaded discharge opening.

The upper wall 4 of the base 1 is provided with an opening 27 thereindefined by an inset flange, upon which is supported the lower housingsection 7 of the motor housing 5, the latter being secured to the base 1by suitable means such as screws 28 passing through respective inwardlydirected projections 29 on the flange 27 and cooperable enlargements 30formed on the lower section 7, for example, four such screws beingemployed, generally symmetrically disposed around the axis of theopening 27, only two of which are illustrated in FIG. 3.

As clearly illustrated in FIG. 3, the respective molded plastic sections6 and 7 of the motor housing 5 are each generally cup-shaped, thesection 6 having a top wall 31 with slightly diverging side walls 32,presenting a more or less conical configuration, which is cemented orsolvent welded at its lower inner peripheral surface to the adjacentexterior support peripheral surface of the side wall 33 of the lowersection 7, which side wall likewise is more or less conicalconfiguration, converging slightly towards the bottom wall thereof whichis formed by a generally conically shaped heat sink plate 34. The outerperipheral edge of the plate 34 may be provided with an outwardlydirected flange 35, embedded in the adjacent wall of the lower section7, while the inner peripheral edge of the heat sink plate, defining acentral circular opening, is provided with a similar flange 36, embeddedin a bearing supporting ring 37. The latter is connected to adjacentside wall portions of the lower section 7 by a plurality of plastic arms39, three such arms being employed in the construction illustrated, onlytwo of which appear in FIG. 3, with the bearing ring 37 and arms 39being formed integrally with and thus of the same plastic material asthe side walls of the lower section 7. Thus, the plate 34 defines thelower wall of the motor housing with the outer surface of the platebeing in direct contact with liquid entering the intake chamber 1'.

The lower housing section 7 may be provided with a plurality ofintegrally pillars or columns 40, illustrated as being three in number,(only two of which are illustrated) and may be circumferentially alignedwith the reenforcing arms or ribs 39, as illustrated. Each pillar 40 isprovided with a generally L-shaped notch 41 in the upper end thereofadapted to receive the adjacent end of the stator core or stack 42 ofthe motor 8, with the stator core being securely retained in radiallyfixed position by the vertically extending portions of the pillars 40disposed adjacent the circumferential face of the core. The latter isrigidly retained in operatively fixed position by a generally cup-shapedbearing cap 43, having a top wall 44 and a cylindrical peripheral wall45, the lower edge of which is, in effect, counterbored to form ashoulder 46 seated on the upper end face of the stator core 42, with thedownwardly depending portion of the side wall 45, at the outer face ofthe core 42, rigidly retaining the cap in radially fixed position on thestator core. The lower section 7, core 42,.and cap 43 are secured inrigid relation by a plurality of motor mounting screws 46, two of whichare adapted to be employed in the embodiment illustrated, with thescrews being disposed adjacent the periphery of the core 42. The lattermay be provided with longitudinally extending notches or grooves in theouter periphery thereof of a size to suitably receive the screws, withthe latter being threaded into respective columns or projections, notillustrated, similar to the projections 30 formed on the lower section7.

Rigidly carried by the drive shaft 24 is a rotor 47, co-

operable with the stator 42, which is adapted to be energized by asuitable field winding 48. The lower end of the shaft 24 is operativelysupported in the bearing ring 37 by a suitable bearing, indicatedgenerally by the numeral 49, comprising an inner race and an outer racehaving suitable ball bearings operatively disposed therebetween, withthe inner race being rigidly secured to the end portion 23, of reduceddiameter, of the drive shaft, for example by means of pressed fit, whilethe outer race is rigidly secured in the retaining ring 37. Asillustrated, the upper end face of the inner bearing race The lower end23 of the shaft 24 is effectively sealed with respect to the passage offluid into or out of the motor housing by a seal, indicated generally bythe reference numeral 51, comprising stationary member 52 which isrigidly mounted in the ring member 37 and provided with a lower annularend face against which a cooperable sealing ring 53 bears, the latterbeing supported on'the end portion 23 of the shaft 24 by a suitable snapor lock ring 54. Effective sealing between the ring 53 and the surfaceof the shaft portion 23 may be effected by a suitable O-ring orcomparable sealing member.

The housing 5 is adapted to contain a suitable quantity of liquidcoolant, as for example, a suitable oil which may also providelubrication for the shaft bearings, with the oil being adapted to becirculated through the housing and around the core structure, etc. byvanes 55 disposed at the lower end of the rotor, the top wall 44 of thebearing cap 43 being suitably provided with a plurality of openings 56,facilitating the desired oil circulation.

As the maximum operational temperature of the motor is considerablyhigher than the temperatures of the liquid to be pumped by thestructure, heat may be withdrawn from the coolant oil, through themetallic heat sink 34, and transferred to the water or liquid beingpumped, for ultimate removal therewith. As the heat sink plate 34 ispreferably of metal having a considerably higher heat conductivecharacteristics than the molded plastic from which the motor housing 5is constructed, considerably improved heat dissipation is achieved.

FIG. 4 illustrates details of the switch housing and associatedstructure, in which the housing 9 comprises a generally cylindrical wall57 which extends downwardly into the intake chamber 1' and is providedadjacent its lower end with an internal shoulder 58 adapted to beengaged by the annular portion of a resilient guard and ceiling memberor diaphragm 59, constructed from synthetic rubber or other suitablematewater to contact the lower wall 62 of the sealing dia- 'phragm foreffecting actuation of the switch 10 when the pressure on the lower wallof the switch sufficiently exceeds air pressure above the switch.

The respective ends of the connector cord 12 and the adjacent end of thepower cord 11 are firmly secured in fluid-tight relation to the motorhousing 5 and switch housing 9, respectively, as illustrated in FIGS. 3and 4. Thus, the connecting cord 12 has its adjacent end extendingthrough the lower wall of a potting well 69, the well being filled, forexample, with a suitable epoxy potting material 70, and the upper end ofthe well being suitably closed by a cord ferrule 71. In like manner, thetop wall of the switch housing 9 is provided with an inverted pottingwell 72, with the adjacent end of the connecting cord 12 extendingthrough the top wall of the switch housing 9 and firmly secured in placein sealed relation by potting material 73 with a suitable cord ferrule74 being disposed at the juncture of the cord 12 with the switchhousing.The adjacent end of the power cord 11 is secured to the switch housing 9in the same manner as the adjacent end of the cord 12.

As illustrated in FIG. 4, the power cord 11 is of special constructionand may include a vent tube 75, which communicates at its adjacent endwith the interior of the switch housing 9 and at its opposite end withan air vent port 76 opening on the side wall of the connecting plug 77of the cord 11.

rial, having a channel 60 formed in the side wall thereof of a size tosnugly receive the peripheral wall portion 61 of the switch 10, therebyforming the mounting means for the switch 10 in the housing, and thesame time providing an effective sealing action of the switch structurewith respect to the housing side wall. The bottom face of the switch isadapted to be sealed by the horizontally extending wall 62 of the member59 which may be provided with anupwardly extending projection 63 adaptedto bear on the adjacent wall of the switch structure. The member 59 andswitch 10 are adapted to be firmly retained in operative position by agenerally cup-shaped switch cap, indicated generally by the numeral 64,which is secured to the base 1 by screws 65 passing through outwardlyextending ears 66 formed on the cap 64, with the screws being threadedAs illustrated in FIGS. 1 and 3, the handle member 13, formed from anysuitable material, for example a relatively stiff synthetic rubber, ismounted directly on the connecting cord 12 and may be, for example,molded directly thereon. As the ends of the connecting cord 12 are veryfirmly secured to the motor housing Sand the switch housing 9, such cordmay be employed as a cooperable part of the handle structure,eliminating the need for additional handle components. Referring to FIG.2, it will be noted that the vertically extending portions of theconnecting cord 12 are disposed substantially on the median line of thepump structure, so that the handle 13 may be considered symmetricallydisposed with respect to the base 1 and the motor housing 5, thedischarge vortex associated elements at least in part counterbalancingthe portions of the switch housing and switch structure disposed at theopposite side of the handle 13.

The pressure responsive switch 10 is illustrated as being of a typeresponsive to pressure differentials on opposite sides thereof, i.e.,closing the operative contacts thereof when the pressure at the bottomface of the switch issufficiently greater than the pressure at the topface thereof, whereby, in operation, the switch will be actuated to aclosed condition when water pressure below the switch reaches apredetermined value. Consequently, testing of the switch may beeffected, in the absence of water pressure below the switch, bysufficiently reducing the air pressure above the switch. This may bereadily accomplished by suitably withdrawing air through the vent tubeto sufficiently reduce the air pressure above the switch to effect atest actuation thereof.

FIG. 4 also illustrates a very simple device for effecting such a testof the electrical circuit of the pump. In the embodiment of theinvention illustrated, the testing device, indicated generally by thenumeral 78, comprises a closed hollow structure comprising two sheets ofmaterial 79a and 79b which may be of like configuration, for examplecircular, and sealed in fluid-tight relation along their peripheralmating edges 80, with the only air inlet and outlet comprising a hollowtube 81 firmly fastened to the sheet 79a and communicating at its innerend with the interior of the structure. The tube may be provided at itsopposite end with a tapering portion 82 of a size to be suitablyinserted in substantially air tight relation in the vent port 76 of theplug 77. Secured to the central portion of the sheet 79b is a manuallygrippable ring 83 carried by a central mounting member 84 secured insealed relation to the sheet 79b. Thus, by effecting separatingmovements between the oppositely disposed walls forrned by the sheets79a and 79b the volume of the interior of the device may be materiallyincreased resulting in an upward flow of air through the tubular stem81. Consequently, tests may be readily made by inserting the end of thestem 81 into the vent port 76 while the structure is in a collapsedcondition as illustrated in FIG. 4, and by effecting relative separatingmovement between the stem 81 and the ring 83, air may be withdrawnthrough the vent tube 75, to sufficiently reduce the air pressure in theupper portion of the switch housing 9 to test actuate the switch 10.

Obviously, the switch 10 will normally be circuited in series with oneof the line conductors, with the opposite side of the switch beingoperatively connected to one side of the field winding 48 through acorresponding conductor in the connecting cord 12, and the other lineconductor ofthe cord 11 being directly connected with the other lineconductor of the cord 12, and connected thereby to the other side of thefield winding 48. The conductors 11 and 12, as well as the plug 77, areillustrated as being of three wire construction with the third wirebeing a ground wire which may be suitably connected to the metallicstructure of the motor 8.

It will be appreciated from the above description that we have providedan exceptionally simple yet highly efficient sump pump constructionparticularly adapted for use as a submerged unit, in which substantiallyall of the main components thereof, other than the necessary metallicparts of the motor structure, may be fabricated as molded plasticcomponents, resulting in an extremely inexpensive yet highly durablestructure that is substantially uneffected by any corrosive or rustingaction of the liquid being pumped.

It will also be noted that we have provided a motor structure employinga novel bearing arrangement, as well as a novel cooling arrangement. Anovel handle structure is also provided making use of the electricalconnecting cord as the connecting supporting structure for the handle.

Having thus described our invention it will be apparent to those skilledin the art that various immaterial modifications may be made in the samewithout departing from the spirit and scope of the invention.

We claim as our invention:

1. A sump pump constructed principally of molded plastic, comprising ahollow molded plastic base, forming a chamber, and having openingstherein for the passage of water from the exterior into the chamber,said base having a water discharge opening therein, a pump structuredisposed in said base chamber having a water inlet opening communicatingwith the chamber interior and a water discharge opening communicatingwith said discharge opening in the base, an electric motor including adrive shaft, a rotor mounted on said drive shaft, a cooperable statorcore and a stator-energizing field winding, a molded plastic motorhousing having a lower housing section and an upper housing section,said housing sections having adjacent mating edge portions connected influid-tight relation to form a closed housing, the opposite end of saidlower section being mounted on said base with the bottom wall of saidlower section extending across an opening in the adjacent wall of saidbase, said lower section being provided with means on which said statorcore is seated in radially fixed relation and with the core axisdisposed vertically, a bearing cap seated upon the upper end of saidstator core in radially fixed relation, means operable to retain saidlower section, stator core and bearing cap in axially fixed relation,said cap and the bottom wall of the lower housing section havingrespective aligned bearing means therein for aligning said drive shaftand rotor on the axis of said stator core, the upper bearing meanscarried by said cap permitting unrestricted axial movement of said shaftand the lower bearing means comprising an outer bearing race fixedlymounted on said bottom wall of the lower section, and a cooperableconcentrically disposed inner bearing race fixedly mounted on said shaftwith said races being operatively connected by a plurality of bearingelements operative to maintain said races in axially fixed relation, andthus support said drive shaft and rotor in operative axially fixedrelation with respect to said stator core, the lower end of said driveshaft extending through said bottom wall into said chamber and throughthe inlet opening of said pump, an impeller mounted on the adjacent endof said shaft and rotatable therewith, seal means, disposed below saidlower hearing, encircling the lower end of said shaft and comprising astationary member carried by said bottom wall of the lower section and acooperable member slidably and rotatably carried by said shaft andengageable with the stationary member to form a fluid seal, axiallyfixed means mounted on said shaft for restricting downward movement ofsaid cooperable member thereon, and means cooperable with saidrestricting means and cooperable member for forming a fluid seal betweenthe latter and said shaft, and or urging said stationary and cooperablemembers in operative engagement, forming a fluid seal between said shaftand said bottom wall, the latter having at least a portion thereofextending across said base opening formed from a material having greaterthermal conductivity than the plastic of said lower section, forming aheat sink operatively disposed between the interior of the motor housingand the base chamber, said bearing cap being provided with the openingstherein, and said drive shaft being provided, adjacent the lower end ofsaid rotor, with a plurality of impeller blades, and a supply of liquidcoolant contained within said motor housing and adapted to circulatetherein by means of said impeller blades, with said heat sink beingoperative to conduct heat from such liquid coolant to the water beingpumped.

2. A sump pump constructed principally of molded plastic, comprising ahollow molded plastic base, forming a chamber, and having openingstherein for the passage of liquid from the exterior into the chamber,said base having a liquid discharge opening therein, a pump structureincluding an impeller, disposed in said base chamber and having a liquidinlet opening communicating with the chamber interior and a liquiddischarge opening communicating with said discharge opening in the base,a closed molded plastic motor housing secured at its lower end to saidbase, an electric motor operatively disposed in said housing andincluding a drive shaft, a rotor mounted on said drive shaft, acooperable stator core, and a stator-energizing field winding, saiddrive shaft extending from said housing into said chamber and havingsaid impeller mounted thereon, said motor housing having a wall portionabutting said chamber and thus is in contact with liquid entering saidchamber, said wall portion being constructed of a material havinggreater thermal conductivity than the plastic of said motor housing,thus forming a heat sink for the conduction of heat developed by saidmotor to the liquid to be pumped, said stator core and field windingbeing inwardly spaced with respect to said wall portion, and said topand side walls of said motor housing, said drive shaft being provided,adjacent the lower end of said rotor, with a plurality of impellerblades, and a supply of liquid coolant contained within said motorhousing in direct contact with said stator core and field winding andsaid wall portion, and adapted to be circulated therearound in the spacebetween the same and said housing, by means of said impeller blades,with said heat sink being operative to conduct heat directly from suchliquid coolant to the water being pumped.

1. A sump pump constructed principally of molded plastic, comprising ahollow molded plastic base, forming a chamber, and having openingstherein for the passage of water from the exterior into the chamber,said base having a water discharge opening therein, a pump structuredisposed in said base chamber having a water inlet opening communicatingwith the chamber interior and a water discharge opening communicatingwith said discharge opening in the base, an electric motor including adrive shaft, a rotor mounted on said drive shaft, a cooperable statorcore and a stator-energizing field winding, a molded plastic motorhousing having a lower housing section and an upper housing section,said housing sections having adjacent mating edge portions connected influid-tight relation to form a closed housing, the opposite end of saidlower section being mounted on said base with the bottom wall of saidlower section extending across an opening in the adjacent wall of saidbase, said lower section being provided with means on which said statorcore is seated in radially fixed relation and with the core axisdisposed vertically, a bearing cap seated upon the upper end of saidstator core in radially fixed relation, means operable to retain saidlower section, stator core and bearing cap in axially fixed relation,said cap and the bottom wall of the lower housing section havingrespective aligned bearing means therein for aligning said drive shaftand rotor on the axis of said stator core, the upper bearing meanscarried by said cap permitting unrestricted axial movement of said shaftand the lower bearing means comprising an outer bearing race fixedlymounted on said bottom wall of the lower section, and a cooperableconcentrically disposed inner bearing race fixedly mounted on said shaftwith said races being operatively connected by a plurality of bearingelements operative to maintain said races in axially fixed relation, andthus support said drive shaft and rotor in operative axially fixedrelation with respect to said stator core, the lower end of said driveshaft extending through said bottom wall into said chamber and throughthe inlet opening of said pump, an impeller mounted on the adjacent endof said shaft and rotatable therewith, seal means, disposed below saidlower bearing, encircling the lower end of said shaft and comprising astationary member carried by said bottom wall of the lower section and acooperable member slidably and rotatably carried by said shaft andengageable with the stationary member to form a fluid seal, axiallyfixed means mounted on said shaft for restricting downward movement ofsaid cooperable member thereon, and means cooperable with saidrestricting means and cooperable member for forming a fluid seal betweenthe latter and said shaft, and or urging said stationary and cooperablemembers in operative engagement, forming a fluid seal between said shaftand said bottom wall, the latter having at least a portion thereofextending across said Base opening formed from a material having greaterthermal conductivity than the plastic of said lower section, forming aheat sink operatively disposed between the interior of the motor housingand the base chamber, said bearing cap being provided with the openingstherein, and said drive shaft being provided, adjacent the lower end ofsaid rotor, with a plurality of impeller blades, and a supply of liquidcoolant contained within said motor housing and adapted to circulatetherein by means of said impeller blades, with said heat sink beingoperative to conduct heat from such liquid coolant to the water beingpumped.
 2. A sump pump constructed principally of molded plastic,comprising a hollow molded plastic base, forming a chamber, and havingopenings therein for the passage of liquid from the exterior into thechamber, said base having a liquid discharge opening therein, a pumpstructure including an impeller, disposed in said base chamber andhaving a liquid inlet opening communicating with the chamber interiorand a liquid discharge opening communicating with said discharge openingin the base, a closed molded plastic motor housing secured at its lowerend to said base, an electric motor operatively disposed in said housingand including a drive shaft, a rotor mounted on said drive shaft, acooperable stator core, and a stator-energizing field winding, saiddrive shaft extending from said housing into said chamber and havingsaid impeller mounted thereon, said motor housing having a wall portionabutting said chamber and thus is in contact with liquid entering saidchamber, said wall portion being constructed of a material havinggreater thermal conductivity than the plastic of said motor housing,thus forming a heat sink for the conduction of heat developed by saidmotor to the liquid to be pumped, said stator core and field windingbeing inwardly spaced with respect to said wall portion, and said topand side walls of said motor housing, said drive shaft being provided,adjacent the lower end of said rotor, with a plurality of impellerblades, and a supply of liquid coolant contained within said motorhousing in direct contact with said stator core and field winding andsaid wall portion, and adapted to be circulated therearound in the spacebetween the same and said housing, by means of said impeller blades,with said heat sink being operative to conduct heat directly from suchliquid coolant to the water being pumped.